Michigan spotted wing Drosophila report for September 3, 2014

This will be the last weekly report of the 2014 spotted wing Drosophila monitoring network. Growers of fall berry crops should continue to monitor and protect susceptible crops where SWD are detected.

This is the eleventh and final weekly report of the Michigan State University Extension spotted wing Drosophila (SWD) statewide monitoring program for 2014. Our network of traps across more than 70 sites was checked during the week of Aug. 28 and shows that SWD activity is continuing to increase in most areas and has been detected at nearly all – 92 percent – of the sites where we are monitoring.

A total of 2,178 male and 1,300 female SWD were trapped, up from 1,598 and 900 the week before, from the following counties in our trapping network: Berrien, Van Buren, Allegan, Kalamazoo, Kent, Ionia, Montcalm, Oceana, Muskegon, Antrim, Leelanau, Grand Traverse, Benzie, Ingham, Genesee, Livingston and Oakland. The average number of SWD per trap increased from 24 last week to 47 this week across the network. Fall red raspberries and late-season blueberries are still at risk for infestation if SWD has been found in monitoring traps on your farm.

Comparison of average trap catches by week between 2013 and 2014.

SWD graph

Comparison of average SWD adults captured per trap by region. This week trapping is reported from 30 sites in the northwest (NW) counties of Antrim, Benzie, Grand Traverse, and Leelanau; 6 sites in the southeast (SE) counties of Ingham, Genesee, Livingston, and Oakland; 44 sites in the southwest (SW) counties of Allegan, Berrien, Kalamazoo, Ottawa, and Van Buren; and 26 sites in the west central (WC) counties of Ionia, Kent, Montcalm, Muskegon, and Oceana.

SWD graph

When SWD are detected in a susceptible crop, tight application intervals are needed to maintain coverage sufficient to protect fruit from SWD. The duration of residual control will vary based on the insecticide, and there are some guides to the length of control you can expect based on recent research in blueberries. This is posted on page 8 of “SWD Management Recommendations for Michigan Blueberry.” When adult SWD are found, new generations are being produced every one to three weeks, depending on weather conditions. In addition to the use of monitoring traps to detect the adult flies, a simple salt solution of 1 cup of salt per gallon of water can be used to assess fruit for larval infestation. Leave the fruit in the solution for a minimum of 15 minutes then check for small, white larvae.

For growers who have completed harvesting susceptible crops, we have not found any benefit to treating plantings for SWD post-harvest, and so we recommend that growers save their time, money and pesticide efficacy for pre-harvest treatments next season. For more information on SWD monitoring and management strategies, and to read past reports, visit MSU‘s Spotted Wing Drosophila website.

The weekly SWD statewide monitoring report has been funded through Project GREEEN and Michigan State University Extension. This output is generated through a network of MSU Extension field staff and campus specialists. We would like to acknowledge the following team members and thank them for their weekly scouting efforts and input into this report: Rufus Isaacs, Keith Mason, Steve VanTimmeren, Larry Gut, Peter McGhee, Michael Haas, Bob Tritten, Mark Longstroth, Brad Baughman, Carlos Garcia, Karen Powers and Nikki Rothwell.

Dr. Isaacs’ work is funded in part by MSU‘s AgBioResearch.

Related Articles